In printing machines which varnish the printed sheets after printing, there is a risk that if printing is interrupted or shut down the varnish liquid remaining on the machine parts which apply varnish to the printed sheets may rapidly stick or dry on these machine parts. Whenever printing is interrupted, this dried varnish must be cleaned or washed from these machine parts.
In some printing machines, such as the machine disclosed in West German Pat. No. 2,608,661, sheets are overprinted, varnished and dried in one gripper operation. In such a machine the varnish feed unit is on the plate cylinder and the varnished sheet passes through a dryer in the same gripper operation. In such a machine, when printing is interrupted, the varnish on the varnishing roller train to the plate cylinder dries fairly rapidly. The dryer heat greatly accelerates the drying process, so that sheets may become stuck to the varnishing rollers even after brief interruptions in continuous printing.